From experimental studies, the following four different types of serum lactate dehydrogenase (LD) isoenzymes have been associated with human malignancies: a) the pattern of increase cathodic LD- isoenzymes frequently observed in solid tumors, b) the pattern of increased intermediate LD-isoenzymes most frequently observed in malignancies of lymphoid cells, c) the pattern of increased anodic isoenzymes which was found in germ cell tumors of the testes, and d) the pattern of super-numerary LD- isoenzymes found in patients with various diseases including cancer. These serum LD-isoenzyme pattern variations can be used as additional parameters to aid diagnosis and treatment of malignant neoplasms in the proper clinical setting (1).